Free-wheeling hub device

ABSTRACT

A freewheel hub device includes two locking rings with axial grooves formed in the locking rings and being essentially V shaped in cross-section. The groove walls of one locking ring form a first and a second wedge surface, and one groove wall of the other locking ring forms a third wedge surface. A roll holder with rolls, which extend into the grooves of the locking rings, is mounted in the locking rings. A hub is rotationally arranged in the roll holder ( 14 ) and has a circumferential surface for cooperation with the rolls. The locking rings and the roll holder are turnable relative to each other in a limited manner and can take three different setting positions relative to each other.

FIELD OF THE INVENTION

The present invention relates to a freewheel hub device, comprising

-   -   a mounting part;    -   a first locking ring means, which is supported by and        non-turnably connected to the mounting part and has a centre        bore and axial inner grooves, whose one side wall forms a first        wedge surface which has a distance, decreasing in one        circumferential direction of the first locking ring means, to        the axis of the centre bore;    -   a lock body holder, which is mounted, in a limited turnable        manner, in the centre bore of the first locking ring means and        supports at least two lock bodies which project radially a        distance from the lock body holder and each extend into a        separate groove of the first locking ring means and which are        movable radially inwards against spring action directed        essentially radially outwards; and    -   a hub, which is rotationally mounted in the lock body holder        coaxially therewith and has a circular-cylindrical        circumferential surface for cooperation with the lock bodies,    -   each lock body, after turning of the lock body holder in said        one direction to a first turning position, abutting against the        associated first wedge surface, which against said spring action        forces the lock body radially inwards in the lock body holder        into engagement with the circumferential surface of the hub,        whereby the hub is prevented from rotating in said one        direction.

BACKGROUND ART

Freewheel hub devices of this type are known in various embodiments, allof which function in such a manner that the hub, when the lock bodyholder is in its first turning position, is prevented from rotating inone direction but can rotate in the other direction.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a freewheel hub devicewhich is adjustable so that it can optionally prevent the hub fromrotating in one direction, allow the hub to rotate in both directions,prevent the hub from rotating in the other direction and also preventthe hub from rotating at all. A special object is to provide a freewheelhub device which is designed so as to be well suited to be mounted on awheelchair to allow, in four optional setting positions, the wheelchairto be driven forwards but not backwards, to be driven forwards as wellas backwards, to be driven backwards but not forwards and not to bedriven forwards or backwards. Easy setting of these different modes offunctioning would facilitate the operation of the wheel-chairsignificantly.

According to the present invention, this object is achieved by afreewheel hub device which is of the type stated by way of introductionand characterised in that

-   -   the other side wall of the axial grooves formed in the first        locking ring means forms a second wedge surface, which has a        distance, decreasing in the other circumferential direction of        the first locking ring means, to the axis of the centre bore,    -   each lock body, after turning of the lock body holder in said        other direction to a second turning position, abutting against        the associated second wedge surface, which against said spring        action forces the lock body radially inwards in the lock body        holder into engagement with the circumferential surface of the        hub, whereby the hub is prevented from rotating in said other        direction,    -   while each lock body, when the lock body holder is in an        intermediate turning position between the first and the second        turning position, is held, by said spring action, disengaged        from the circumferential surface of the hub, so that the hub is        rotatable in both directions,    -   that the device further comprises a second locking ring means        which is concentric with the first locking ring means and has a        centre bore and axial inner grooves, whose one side wall forms a        third wedge surface which has a distance to said axis, which        decreases in said one direction,    -   the lock body holder being mounted in a limited turnable manner        in the centre bore of the second locking ring means in such a        manner that its lock bodies each extend into a separate groove        of the second locking ring means,    -   each lock body, when the lock body holder and the second locking        ring means are in a first mutual turning position after turning        of the second locking ring means in said other direction        relative to the lock body holder, abutting against the        associated third wedge surface, which against said spring action        forces the lock body radially inwards in the lock body holder        into engagement with the circumferential surface of the hub,        whereby the hub is prevented from rotating in said one        direction.

In a preferred embodiment, a first spring is arranged to bias the lockbody holder in said one direction in such a manner that it takes itsfirst turning position, in which each lock body abuts against theassociated first wedge surface.

In another preferred embodiment, the lock body holder and the secondlocking ring means are biased relative to one another by means of asecond spring in such a manner that they take a second mutual turningposition, from which the second locking ring means is, against theaction of the second spring, turnable in said other direction relativeto the lock body holder to said first mutual turning position.

The freewheel hub device advantageously has an actuating ring, which isconcentric with the locking ring means and the lock body holder and isnon-turnably connected to the second locking ring means and connected tothe lock body holder in a limited turnable manner, wherein,

-   -   when the device is in a starting position, in which the lock        body holder is held by the first spring in its first turning        position and the lock body holder and the second locking means        are held by the second spring in their second mutual turning        position and the hub thus is rotatable in said other direction        but is prevented from rotating in said one direction,    -   the lock body holder, by turning of the actuating ring in said        other direction, is turnable to its intermediate turning        position, in which the hub is rotatable in both directions, and        by continued turning of the actuating ring in said other        direction is turnable to its second turning position, in which        the hub is rotatable in said one direction but is prevented from        rotating in said other direction and in which the lock body        holder by the abutment of the lock bodies against the associated        second wedge surfaces is prevented from being turned further in        said other direction, the second locking ring means, in further        continued turning of the actuating ring in said other direction,        being turnable, against the action of the second spring, in said        other direction relative to the lock body holder to said first        mutual turning position, in which the hub is also prevented from        rotating in said one direction and thus is completely locked.

The actuating ring may have a radially projecting actuating arm forturning of the actuating ring, in which case the actuating arm can beconnected to a wire.

The lock bodies preferably consist of rolls, whose axes are parallelwith said axis.

The mounting part may be adapted to be mounted on a wheelchair frame, inwhich case the hub has means for non-turnable connection of the hub anda wheel-chair wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail by means of anembodiment and with reference to the accompanying drawings.

FIG. 1 is an exploded view and shows a freewheel hub device according tothe present invention.

FIG. 2 shows a roll holder included in the freewheel hub deviceaccording to FIG. 1, with a hub inserted.

FIG. 3 shows the freewheel hub device according to FIG. 1 in anassembled state and with some parts broken away.

FIG. 4 shows a first locking ring included in the freewheel hub deviceaccording to FIG. 1.

FIG. 5 shows a second locking ring included in the freewheel hub deviceaccording to FIG. 1.

FIGS. 6-9 illustrate the position of the roll holder in relation to thefirst and the second locking ring in four different setting positions ofthe freewheel hub device.

FIG. 10 shows a wheelchair provided with a freewheel hub deviceaccording to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

The freewheel hub device shown in the drawings has a mounting part 1 inthe form of an essentially rectangular aluminium plate with a throughhole 2. The mounting part 1 has three circular recesses 3-5 concentricwith the hole 2 and arranged in steps, viz. an outer recess 3, anintermediate recess 4 formed therein and an inner recess 5 locatedadjacent to the hole 2 and formed in the intermediate recess 4. A brasswasher 6 is placed in the inner recess 5. The thickness of the washer 6approximately equals the depth of the inner recess 5. A sleeve-shapedbearing bolt 7 for holding, for instance, a wheel axle journal extendsthrough the hole 2 and abuts against the washer 6 by means of acircumferential shoulder 8. A nut (not shown) is screwed onto thethreaded portion 9 of the bolt 7 and clamps the bolt 7 against thewasher 6, which prevents the bolt from rotating.

Two identical locking rings 10, which are made of hard sheet steel bypunching, together form a first locking ring means. The locking rings 10have a combined thickness which equals the depth of the outer recess 3,and an outer diameter which equals the diameter of the outer recess 3,and are arranged in the outer recess 3. Each locking ring 10 has alaterally extending protrusion 11, which is fitted into acorrespondingly formed expansion 12 of the outer recess 3 and is thusheld non-turnably in the mounting part 1. Each locking ring 10 has aninner diameter which is somewhat greater than the diameter of theintermediate recess 4. Each locking ring 10 further has four axialgrooves 13 which are uniformly distributed along the inner circumferenceand are V-shaped in cross-section with a V angle of about 140° (see FIG.4). One side wall of each groove 13 forms a first wedge surface 13 a andits other side wall forms a second wedge surface 13 b.

An essentially circular-cylindrical roll holder 14, which is shown inmore detail in FIG. 2, supports four lock bodies in the form of rolls15. The outer diameter of the roll holder 14 is somewhat smaller thanthe inner diameter of the locking rings 10. The roll holder 14 has atits side facing the mounting part 1 a bottom plate 16 with a centre bore17. The roll holder 14 also has an inner rim 18 which surrounds thecentre bore 17 and whose inner diameter is greater than the diameter ofthe centre bore. The inner rim 18 is divided into four sections whichare uniformly distributed in the circumferential direction and betweenthem form openings 19 whose extent in the circumferential direction atthe inside of the rim sections is smaller than the diameter of the rolls15. The roll holder 14 also has an outer rim 20 which defines the rollholder 14 outwards and which together with the inner rim 18 defines anannular groove 21 in the roll holder 14. The outer rim 20 is, like theinner rim 18, divided into four sections which are uniformly distributedin the circumferential direction and between them form openings 22 whichare positioned opposite to the openings 19 in the inner rim 18. Theextent of the openings 22 in the circumferential direction at theoutside of the outer rim sections is smaller than the diameter of therolls 15. The rolls 15 are each placed in one of the compartments whichare formed by the openings 19 and 22 in the rims 18 and 20. The rolls 15are arranged in these compartments in such a manner that their axes areparallel with the axis of the centre bores 2 and 17.

Four circular-arc-shaped spring elements 23 of elastic material, such aspolyurethane, are arranged in the annular groove 21 and each abut attheir ends against two rolls 15. The spring elements 23 are kept inplace by means of protrusions 24 which extend radially inwards from theouter rim 20 and which engage in a corresponding recess in therespective spring elements 23. The spring elements 23 force the rolls 15radially outwards.

An axially directed threaded hole 25 is formed in three of the foursections of the outer rim 20. A pin 26 is screwed into one of theseholes 25. A spacer sleeve 27 is arranged round each of the two otherholes 25.

A locking ring 28, which is made of hard steel sheet by punching, formsa second locking ring means. The locking ring 28 has an inner diameterwhich is the same as the inner diameter of the locking rings 10, i.e.equal to the outer diameter of the roll holder 14, and an outer diameterwhich is slightly smaller than the outer diameter of the locking ring10. The locking ring 28 has four axial grooves 29, which are uniformlydistributed along the inner circumference and which are V shaped incross-section with a V angle of about 140° (see FIG. 5). One side wallof each groove 29 forms a third wedge surface 29 a. The locking ring 28has a radially projecting arm 30 with a through hole 31.

The locking ring 28 abuts against one of the locking rings 10 andsurrounds, like these, the roll holder 14. The locking rings 10 and 28and the roll holder 14 are arranged in such a mutual turning positionthat the rolls 15 are located essentially opposite to the grooves 13 and29. The rolls 15 extend a distance into the grooves 13 and 29 by beingforced radially outwards by the spring elements 23.

The shown freewheel hub device further has an actuating ring 32, whichhas a somewhat smaller outer diameter than the second locking ring 28,and an inner diameter which is equal to the outer diameter of the innerrim 18 of the roll holder 14. The actuating ring 32 is turnably arrangedon the inner rim 18. The actuating ring 32 has a radially projectingactuating arm 33 with a through hole 34. An internally threaded,sleeve-shaped pin 35 extends through the hole 31 in the arm 30 of thesecond locking ring 28 and through the hole 34 in the arm 33 of theactuating ring 32, and a screw 36 is screwed into the sleeve-shaped pin35. The actuating ring 32 and the second locking ring 28 are thusnon-turnably connected to each other.

The actuating arm 32 has a further through hole 37, in which one end ofa tension spring 38 is fixed. The other end of the tension spring 38 isfixed to a screw 39 which is screwed into a hole 40 in the vicinity ofone of the corners of the mounting part 1. The tension spring 38 biasesthe actuating ring 32 and, thus, the second locking ring 28 in oneturning direction A (clockwise with regard to FIG. 1).

The actuating ring 32 has three through holes 41 each locatedessentially opposite to one of the three threaded holes 25 in the outerrim 20 of the roll holder 14. The holes 41 are elongate in thecircumferential direction. The pin 26 fixed to the outer rim 20 of theroll holder 14 extends through one of the holes 41. Two screws 42 eachextend through one of the two other holes 41 and are screwed intocorresponding holes 25 in the outer rim 20 of the roll holder 14. Oneend of a tension spring 43 is fixed to the pin 26 and the other end isfixed to a pin 44 which is fixed to the actuating ring 32 and which isarranged relative to the pin 26 in such a manner that the tension spring43 strives to turn the roll holder 14 relative to the actuating ring 32in the turning direction B opposite to said one turning direction A. Asa result, the pin 26 and the two screws 42 abut against one terminaledge of the respective holes 41.

A sleeve-shaped hub 45 has a first hub portion 46 whose outercircumference is essentially equal to the inner diameter of the innerrim 18 and by means of which the hub 45 is rotatably mounted in the rollholder 14. The circular-cylindrical circumferential surface 47 of thefirst hub portion 46 cooperates with the rolls 15 in the roll holder 14.The hub 45 also has a second hub portion 48 which has a smaller outerdiameter than the first hub portion 46 and which is divided into twohalves by means of two diametrically opposed axial slots 49.

Two spring washers 50, which each have two diametrically opposedprojections 51 extending radially inwards are slipped onto the secondhub portion 48 and rest against the first hub portion 46. Theprojections 51 each engage in a slot 49 so that the spring washers 50are non-turnably connected to the hub 45.

A coupling ring 52, which has two diametrically opposed projections 53extending radially inwards, is in the same way as the spring washers 50non-turnably arranged on the second hub portion 48. The spring washers50 and the coupling ring 52 are held on the hub 45 by means of aretaining ring 54 which engages in a circumferential groove (not shown)formed in the second hub portion 48. The spring washers 50 press thecoupling ring 52 into engagement with the retaining ring 54. Thecoupling ring 52 has the form of a toothed wheel with teeth 55 directedaxially away from the first hub portion 46.

The hub 45 is rotationally mounted on that portion 56 of thesleeve-shaped bearing bolt 7 which defines the bearing bolt shoulder 8abutting against the brass washer 6. The roll holder 14 is also mountedon this portion 56.

The coupling ring 52 is arranged to be non-turnably connected to acorresponding coupling ring (not shown) which is non-turnably connectedto a wheel whose journal is mounted in the bearing bolt 7.

The shown freewheel hub device further has an operating cable or wire 57which is attached in a transverse hole 58 in the sleeve-shaped pin 35.

FIGS. 6-9 illustrate the position of the roll holder 14 and, thus, ofthe rolls in relation to on the one hand the locking rings 10 (in theupper part in each Figure) and, on the other hand, the locking ring 28(in the lower part in each Figure) in four different setting positionsof the freewheel hub device described above.

FIG. 6 shows the starting position of the freewheel hub device, in whichthe roll holder 14 is held by the spring 38 in a first turning positionrelative to the mounting part 1 and is held by the spring 43 in a secondmutual turning position relative to the locking ring 28. In the firstturning position of the roll holder 14 the rolls 15 abut against therespective first wedge surfaces 13 a of the first locking rings 10. Thewedge surfaces 13 a force, against the action of the spring elements 23,the rolls 15 radially inwards in the roll holder 14 into engagement withthe circumferential surface 47 of the hub 45, whereby the hub isprevented from rotating in said one direction A. At the same time theroll holder 14 is, as mentioned above, in its second mutual turningposition relative to the locking ring 28, in which the rolls 15 arepositioned in the respective grooves 29 in the locking ring 28 withoutabutting against any one of the side walls of the groove. In thestarting position of the freewheel hub device, the hub 45 can thusrotate in said direction B but is prevented from rotating in saiddirection A.

When the actuating ring 32 is turned by means of the wire 57 in saiddirection B against the action of the spring 38, also the locking ring28 which is non-turnably connected to the actuating ring 32 and the rollholder 14 connected to the actuating ring 32 by means of the spring 43are turned in this direction. The roll holder 14 then first reaches anintermediate turning position relative to the mounting part 1, which isshown in FIG. 7 and in which the rolls 15 are positioned in therespective grooves 13 in the locking rings 10 without abutting againstany one of the side walls of the groove. At the same time the rollholder 14 is still located in its second mutual turning positionrelative to the locking ring 28. The rolls 15 are held by the springelements 53 disengaged from the circumferential surface 47 of the hub45, so that the hub can rotate in both directions A and B.

In continued turning of the actuating ring 32 in said direction B, theroll holder 14 reaches a second turning position relative to themounting part 1, which is shown in FIG. 8 and in which the rolls 15 abutagainst the respective second wedge surfaces 13 b of the locking rings10. The wedge surfaces 13 b force, against the action of the springelements 23, the rolls 15 radially inwards into engagement with thecircumferential surface 47 of the hub 45, whereby the hub is preventedfrom rotating in said direction B. At the same time the roll holder 14is still located in its second mutual turning position relative to thelocking ring 28. Thus the hub 45 can rotate in said direction A but isprevented from rotating in said second direction B.

In still continued turning of the actuating ring 32 in said direction B,the roll holder 14 is no more carried along since it is stopped owing tothe abutment of the rolls 15 against the respective second wedgesurfaces 13 b of the locking rings 10. The roll holder 14 is thussecured, which means that the actuating ring 32 and, thus, the lockingring 28 turn, against the action of the spring 43, in said seconddirection B relative to the roll holder 14, which is allowed by theholes 41 in the actuating ring being elongate. The roll holder 14 willtake a first mutual turning position relative to the locking ring 28, inwhich the rolls 15 abut against the respective third wedge surfaces 29 aof the locking ring 28. The wedge surfaces 29 a force, against theaction of the spring elements 23, the rolls 15 radially inwards in theroll holder 14 into engagement with the circumferential surface 47 ofthe hub 45, whereby the hub 45 is also prevented from rotating in saiddirection A and consequently, is completely locked.

The above described freewheel hub device is shown in FIG. 10 mounted onthe right side of the frame 61 of a wheelchair 60. A correspondingfreewheel hub device is conveniently also mounted in the same way on theleft side of the wheelchair 60. The wheels 62 of the wheel-chair 60 havea journal 63 which is mounted in the bearing bolt 7 of the freewheel hubdevice. A coupling ring (not shown) which corresponds to the couplingring 52 and which is non-turnably connected to the wheel 62 isnon-turnably connected to the coupling ring 52 and, hence, to the hub45. The operating wire 57 of the freewheel hub device is at its free endfixed to a setting mechanism 64, which has a setting lever 65 pivotingon a transverse shaft. The lever 65 is in FIG. 10 shown in its rearposition, which corresponds to the starting position of the freewheelhub device. In the position of the lever 65 shown in FIG. 10, the wheel62 of the wheelchair 60 is thus freely rotatable in said seconddirection B (counterclockwise in FIG. 10), i.e. backwards, but cannotrotate in the opposite direction, i.e. forwards. When pivoting the lever65 one step forward, a position is obtained, in which the wheel 62 isfreely rotatable in both directions. When pivoting the lever 65 one morestep forwards, a position is obtained, in which the wheel 62 is freelyrotatable in said direction A (clockwise in FIG. 10), i.e. forwards, butcannot rotate in the opposite direction, i.e. backwards. When pivotingthe lever 65 one more step forwards, a position is obtained, in whichthe wheel 62 is completely locked and cannot rotate in any direction.

1. A freewheel hub device, comprising a mounting part (1); a firstlocking ring means (10), which is supported by and non-turnablyconnected to the mounting part and has a centre bore and axial innergrooves (13), whose one side wall forms a first wedge surface (13 a)which has a distance, decreasing in one circumferential direction (A) ofthe first locking ring means, to the axis of the centre bore; a lockbody holder (14), which is mounted, in a limited turnable manner, in thecentre bore of the first locking ring means (10) and supports at leasttwo lock bodies (15) which project radially a distance from the lockbody holder and each extend in a separate groove (13) of the firstlocking ring means (10) and which are movable radially inwards againstspring action directed essentially radially outwards; and a hub (45),which is rotationally mounted in the lock body holder (14) coaxiallytherewith and has a circular-cylindrical circumferential surface (47)for cooperation with the lock bodies (15), each lock body (15), afterturning of the lock body holder (14) in said one direction (A) to afirst turning position, abutting against the associated first wedgesurface (13 a), which against said spring action forces the lock bodyradially inwards in the lock body holder into engagement with thecircumferential surface (47) of the hub (45), whereby the hub isprevented from rotating in said one direction (A), characterised in thatthe other side wall of the axial grooves (13) formed in the firstlocking ring means (10) forms a second wedge surface (13 b), which has adistance, decreasing in the other circumferential direction (B) of thefirst locking ring means, to the axis of the centre bore, each lock body(15), after turning of the lock body holder (14) in said other direction(B) to a second turning position, abutting against the associated secondwedge surface (13 b), which against said spring action forces the lockbody radially inwards in the lock body holder into engagement with thecircumferential surface (47) of the hub (45), whereby the hub isprevented from rotating in said other direction (B), while each lockbody (15), when the lock body holder (14) is in an intermediate turningposition between the first and the second turning position, is held, bysaid spring action, disengaged from the circumferential surface (47) ofthe hub (45), so that the hub is rotatable in both directions (A and B),that the device further comprises a second locking ring means (28) whichis concentric with the first locking ring means (10) and has a centrebore and axial inner grooves (29), whose one side wall forms a thirdwedge surface (29 a) which has a distance to said axis, which decreasesin said one direction (A), the lock body holder (14) being mounted in alimited turnable manner in the centre bore of the second locking ringmeans (28) in such a manner that its lock bodies (15) each extend into aseparate groove (29) of the second locking ring means, each lock body(15), when the lock body holder (14) and the second locking ring means(28) are in a first mutual turning position after turning of the secondlocking ring means in said other direction (B) relative to the lock bodyholder, abutting against the associated third wedge surface (29 a),which against said spring action forces the lock body radially inwardsin the lock body holder into engagement with the circumferential surface(47) of the hub (45), whereby the hub is prevented from rotating in saidone direction (A).
 2. A freewheel hub device as claimed in claim 1, inwhich a first spring (38) is arranged to bias the lock body holder (14)in said one direction (A) in such a manner that it takes its firstturning position, in which each lock body (15) abuts against theassociated first wedge surface (13 a).
 3. A freewheel hub device asclaimed in claim 1, in which the lock body holder (14) and the secondlocking ring means (28) are biased relative to one another by means of asecond spring (43) in such a manner that they take a second mutualturning position, from which the second locking ring means is, againstthe action of the second spring, turnable in said other direction (B)relative to the lock body holder to said first mutual turning position.4. A freewheel hub device as claimed in claim 1, which has an actuatingring (32), which is concentric with the locking ring means (10,28) andthe lock body holder (14) and is non-turnably connected to the secondlocking ring means (28) and connected to the lock body holder in alimited turnable manner, wherein, when the device is in a startingposition, in which the lock body holder (14) is held by the first spring(38) in its first turning position and the lock body holder (14) and thesecond locking means (28) are held by the second spring (43) in theirsecond mutual turning position and the hub (45) thus is rotatable insaid other direction (B) but is prevented from rotating in said onedirection (A), the lock body holder (14), by turning of the actuatingring (32) in said other direction (B), is turnable to its intermediateturning position, in which the hub (45) is rotatable in both directions(A and B), and by continued turning of the actuating ring (32) in saidother direction (B) is turnable to its second turning position, in whichthe hub (45) is rotatable in said one direction (A) but is preventedfrom rotating in said other direction (B) and in which the lock bodyholder (14) by the abutment of the lock bodies (15) against theassociated second wedge surfaces (13 b) is prevented from being turn-edfurther in said other direction (B), the second lock-ing ring means(28), in further continued turning of the actuating ring (32) in saidother direction (B), being turnable, against the action of the secondspring (43), in said other direction (B) relative to the lock bodyholder (14) to said first mutual turning position, in which the hub (45)is also prevented from rotating in said one direction (A) and thus iscompletely locked.
 5. A freewheel hub device as claimed in claim 4, inwhich the actuating ring (32) has a radially projecting actuating arm(33) for turning of the actuating ring.
 6. A freewheel hub device asclaimed in claim 5, in which the actuating arm (33) is connected to awire (56).
 7. A freewheel hub device as claimed in claim 1, in which thelock bodies (15) con-sist of rolls whose axes are parallel with saidaxis.
 8. A freewheel hub device as claimed in claim 1, in which themounting part (1) is adapted to be mounted on a wheelchair frame (61)and the hub (45) has means (52) for non-turnable connection of the huband a wheelchair wheel (62).